How do you determine the sign of the answer?

If there are more positives, than negatives, your answer will always be postive.

If there are more negatives, than positives, your answer will always be negative.

I really hopes it right. Have a good day!

for finding the midpoint of any given 2 pair of points simply add the respective x coordinates with other x coordinate and the y coordinate with other y coordinate and divide them by 2

in your question it will be :

(3+1)/2 for the x coordinate of mid point i.e 2

[8+(-4)]/2 for the y coordinate of midpoint i.e 2

so coordinates of mid point of points (3,8) and (1,-4) will be (2,2)